which is the #1 travel destination in south america?

I'm guessing Brasil - due to its size and variety of places to see and things to do - that's where I'd go

Country or place? Machu Picchu would be the most visited site in South America.

I am biased towards Peru. It all depends on one's interests.
I have not been to anywhere else in South America so it is hard for me to compare...impossible, that is.
However, I can honestly tell you that I like Peru so much and my experiences there are so memorable that I wish to return for another visit if I can afford it.

Macchu Picchu is definately Number 1

The best beaches are in Punta del Este, Uruguay or in Bahia, Brazil. As far as mountains is concerned, go to Chile, Argentina and the views are breathtaking !